how aarch32 jump to aarch64

[yoma sophian]

hi arnd:

2015-06-15 9:19 GMT+08:00 yoma sophian <sophian.yoma at gmail.com>:
> hi Arnd:
>
> 2015-06-15 3:39 GMT+08:00 Arnd Bergmann <arnd at arndb.de>:
>> On Sunday 14 June 2015 23:06:49 yoma sophian wrote:
>>> hi all:
>>> as far as I know, we can use pseudo eret to let aarch64 jump to aarch32.
>>> But how could we let aarch32 --> aarch64?
>>>
>>
>> I believe the only way is to trap into a higher privilege level, e.g. from
>> user space to the kernel, or from kernel into hypervisor mode. If you
>> want to implement mode switching within one binary, you would then add
>> a syscall/hypercall/... that returns without switching back to aarch32.
> Do you mean to use HVC, SVC, in aarch32?
> But as far as I remember, they are exception instructions which let
> processor jump to aarch32 hypervisio, and aarch32 supervisor mode
> seperately.
> Is there any exception instruction which will let aarch32 jump to aarch64?
in so far aarch64 kernel enviornemnt, the kernel is running in
Ns-aarch64-EL1 and user mode support aarch32 binary.
so there should be some instruction, which can let processor jump from
aarch32 --> aarch64, right?

appreciate your help,